Asphalt road paving machines (or asphalt pavers) include a tractor with a hopper for receiving asphalt paving material located at the front of the paver, and a feeder conveyor for delivering the asphalt paving material to the rear of the paver to a spreader auger. The auger distributes the asphalt laterally behind the tractor to the road surface in front of the screed.
Asphalt pavers include a screed, a heavy assembly drawn behind the paving machine by a pair of pivotally mounted tow arms for smoothing out and compressing the asphalt material. Pavers may include a screed extender frame for adjusting screed width, which may be hydraulically adjustable.
Road mat thickness is determined in part by asphalt material composition, machine specifics, as well as by the volume of the asphalt material pile placed in front of the screed. Asphalt material composition and screed specifics are typically constants with a specific machine and mix; however, the height of the material pile must be continuously provided by the conveyor and auger as the paver moves forward. Material pile height should remain constant to pave an even surface. Variables affecting a current material pile size include the conveyor speed, and the auger speed.
Sensors mounted on the end of the screed or screed extender help determine the amount of material in front of the screed. The machine operator may manually set estimated material height, or provide an estimated control gain by using a marked dial or digital input on the control panel, to direct the machine to regulate the material pile to a target size using the auger and conveyor systems.
Too much material placed in front of the screed results in a ridge once the machine is adjusted to the proper material pile height. Too little material placed in front of the screed results in a dip once the machine is adjusted to the proper material pile height. Some paving machines utilize manual knobs that an operator turns to adjust the gain for a paver to set the target material pile height. This gain signals to an electronic control module (ECM) as to the material height setting, and thus, the conveyor and auger speed.
U.S. Pat. No. 5,575,583 to Grembowicz et al. describes an apparatus for controlling a material feed system. The apparatus includes a sensor that monitors the amount of material at the edge of the screed and responsively produces a target material height signal, which the operator matches using a rotary switch. It is desirable to provide a system that can provide the proper settings from initial paving. It may also be desirable to automate the process to reduce variability due to operator subjectivity.